<!doctype html>
<html>
<head>
<meta charset="utf-8">
<title>嵌套中的清除浮动</title>
<style>
	#box:after{ content:"_css"; }
	#box:before{ content:"say:"; }	
</style>
</head>
<body>
<div id="box">hello</div>
</body>
</body>
</html>




